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Message-ID: <1272783032.2173.8.camel@edumazet-laptop> Date: Sun, 02 May 2010 08:50:32 +0200 From: Eric Dumazet <eric.dumazet@...il.com> To: David Miller <davem@...emloft.net> Cc: netdev@...r.kernel.org, therbert@...gle.com, hadi@...erus.ca Subject: Re: [PATCH net-next-2.6] net: eth_type_trans() should inline skb_pull() Le samedi 01 mai 2010 à 18:15 -0700, David Miller a écrit : > From: Eric Dumazet <eric.dumazet@...il.com> > Date: Sat, 01 May 2010 08:42:25 +0200 > > > [PATCH net-next-2.6] net: eth_type_trans() should inline skb_pull() > > > > With RPS, this patch can give a 5 % boost in performance. > > > > Signed-off-by: Eric Dumazet <eric.dumazet@...il.com> > > Awesome, but let's do this in a way that allows us to easily annotate > where inlining makes sense in other places, not just here. > > Something like this, ok? > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index 82f5116..746a652 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -1128,6 +1128,11 @@ static inline unsigned char *__skb_pull(struct sk_buff *skb, unsigned int len) > return skb->data += len; > } > > +static inline unsigned char *skb_pull_inline(struct sk_buff *skb, unsigned int len) > +{ > + return unlikely(len > skb->len) ? NULL : __skb_pull(skb, len); > +} > + > extern unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta); > > static inline unsigned char *__pskb_pull(struct sk_buff *skb, unsigned int len) > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index 4218ff4..8b9c109 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -1051,7 +1051,7 @@ EXPORT_SYMBOL(skb_push); > */ > unsigned char *skb_pull(struct sk_buff *skb, unsigned int len) > { > - return unlikely(len > skb->len) ? NULL : __skb_pull(skb, len); > + return skb_pull_inline(skb, len); > } > EXPORT_SYMBOL(skb_pull); > > diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c > index 0c0d272..61ec032 100644 > --- a/net/ethernet/eth.c > +++ b/net/ethernet/eth.c > @@ -162,7 +162,7 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev) > > skb->dev = dev; > skb_reset_mac_header(skb); > - skb_pull(skb, ETH_HLEN); > + skb_pull_inline(skb, ETH_HLEN); > eth = eth_hdr(skb); > > if (unlikely(is_multicast_ether_addr(eth->h_dest))) { Excellent ! Changli privately asked me why we were ignoring cases where skb->len < ETH_HLEN. I replied that minimum frame size was 46+12, then he asked me why we were testing another time : if (skb->len >= 2 && *(unsigned short *)rawp == 0xFFFF) return htons(ETH_P_802_3); Could we assume all eth_type_trans() must call it with initial skb->len >= (46 + 12) or not ? (According to ethernet specs, all frames should have a minimum payload of 46 bytes) If not sure, maybe we should issue a WARN_ON_ONCE() If yes, tests could be removed and we could gain two cycles ;) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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